The Webley flare gun was rented from Bapty and after the filming for ESB ended, the weapon was stripped down and returned to them. The only sources of the blaster are the promo photos and the screencaps ==> Boba Fett The Empire Strikes Back. There was a casting of the gun dressed as the ESB version on some of the ESB promo/touring suit, especially the one with the Pre-Pro #1 helmet:
once again amazed by you knowledge Raf would be nice to think bits of it were in a box somewhere in storage so sad not much of the ESB costume survives especially the jetpack i read on here it got stolen >?
I don't know if the ESB jetpack was stolen (we only knew about the Pre-Pro #2 helmet and jetpack), but most of the armor parts were repainted for ROTJ, while the soft parts (flightsuit, vest, boots and braids) were used without major modifications for ROTJ and later for ROTJ SE. More info here regarding the reused hard parts for ROTJ ==> The Fate Of The Twin Armors: Pre-Pro #1, Pre-Pro #3 and ESB (a bit outdated, but still a good read, I think).